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High risk in actual traffic demand often causes a serious imbalance in interests between the public and private sectors in transportation public–private partnership (PPP) projects. The part...

Public-private partnership (PPP) is an alternative and efficient method to financing infrastructure provisions such as sewage treatment and water facilities. The long-term contract and dynamic uncertainty lead to inevitable and high-incidence renegotiation to PPP. However, renegotiation has been recognized as the Achilles' heel of concessions. The renegotiation initiated by the concessionaire in the construction phase usually occurs when the actual construction costs are higher than predicted. To explore when the concessionaire initiates renegotiation and the dynamic evolution tendency of his/her renegotiation behavior when actual construction costs overrun in the PPP sewage treatment project, this paper introduces the fluctuation of construction costs as a quantitative index and establishes an evolutionary game model to analyze the best strategic choice of the concessionaire under different circumstances. The not-renegotiating and renegotiating thresholds of the concessionaire can be drawn based on the model. According to these two thresholds, the fluctuation range of construction costs can be divided into three intervals. This article further discusses the evolution of the concessionaire's renegotiation behavior when the fluctuation of construction costs lies in these three different intervals. The findings indicate that when the actual construction costs overrun in the PPP sewage treatment, the best strategic choice of the concessionaire in the cooperation dilemma is related to the fluctuation of the construction costs. The results reveal the nonlinear relationships between renegotiation behavior and fluctuation in construction costs and provide a reference for regulating PPP renegotiation behavior in the construction stage to reduce its incidence.

Urban rail transit is a quasioperational project and its net cash inflow can hardly cover the investment expenditure. It is essential to determine an acceptable amount of government subsidy to ensure the financial viability of the PPP projects, so as to encourage the entry of the private partner. The partners involved in PPPs have common interests but conflict regarding the value of government subsidy. Considering the uncertainty characteristic by PPPs and information incompleteness in the decision-making process, this study presents a methodology to calculate the equitable subsidy ratio favored by both participants. This study divides the decision process into two steps. First, this study constructs a financial model and introduces an acceptable range of subsidy ratio by using the Monte Carlo simulation method. Second, this study uses the bargaining game theory to determine a particular subsidy ratio under incomplete information. To verify the applicability of the presented model, the researchers invoke an illustrative example for model validation. This research provides a referential and operational method for the government and private sectors to make government subsidy decisions for quasioperational projects.

The transactions related to real estate in social and economic activities need to appraise the market value of commercial housing. In order to improve the accuracy and efficiency of mass appraisal model (MA), the paper proposed the Improved-GBDT algorithm based on hybrid feature selection, which combines the concept of supervised learning and unsupervised learning, selecting appropriate features based on the impact of features on results and the changing trend of feature data. The feature weights can be calculated by Random Forest and XGBoost. Considering grey correlation analysis, the correlation degree among features can be calculated, and appropriate features can be selected. In the paper, we took the housing sales data from May 2014 to May 2015 in USA into simulation analysis. The simulation results show that IGBDT model has better accuracy and stability than SVR, RF and XGBoost. Compared with RF and XGBoost model under optimal parameters, IGBDT not only reduced the average absolute error of prediction by 98% and 11%, but also make the maximum relative error drop by 97% and 12%. The results show that IGBDT can provide a powerful reference in evaluating the property market value.

A modified Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method based on the dispersive solid-phase extraction (dSPE) combined with high-performance liquid chromatography (HPLC) was developed for the determination of thiabendazole (TBZ) in environmental and food samples. Hydroxyl functionalized multiwalled carbon nanotube (MWCNT-OH) was used as dSPE material for the preconcentration of analyte. Several experimental parameters, including the amount of sorbent, extraction time, the pH and ionic strength of sample solution, and desorption conditions, were evaluated. Under optimal experimental conditions, good linearity was observed in the range of 10–1000 ng mL−1 with the correlation coefficient of 0.9962. The limit of detection and quantification were 2.6 and 8.7 ng mL−1, respectively. The present method was applied to the analysis of different environmental and food samples, and the recoveries of TBZ obtained were in the range of 92.9–103.9 % with the relative standard deviations lower than 6.5 %. The results showed that the proposed method was a rapid, convenient, and feasible method for the determination of TBZ in environmental and food samples.

Bisphenol AF (BPAF) was used as a model compound to investigate the binding mechanism between the endocrine disrupting compound and human serum albumin (HSA) using multispectroscopic techniques and molecular modeling method at the protein level. The results indicated that BPAF was indeed bound to HSA and located in the hydrophobic pocket of HSA on subdomain IIA through hydrogen bond and van der Waals interactions. The fluorescence quenching data showed that the binding of BPAF and HSA quenched the intrinsic fluorescence of HSA, and the static quenching constants were acquired.

Recent studies have shown the presence of endocrine disrupting compounds (EDCs) in surface water and sewage samples. A study on rapid removal of endocrine disrupting compounds (EDCs)-bisphenol AF (BPAF) on multi-walled carbon nanotube (MWCNT) is significant for understanding how wastewater containing trace recalcitrant or hazardous BPAF was treated. Besides, the sorption behavior and mechanisms remain largely unknown. In this study, it was found the adsorption kinetics equilibrium followed the pseudo-second-order model, while the adsorption isotherms fitted better with Langmuir equation, and the adsorption is a spontaneous and exothermic process. The adsorption process was controlled simultaneously by external mass transfer and intraparticle diffusion, but the external mass transfer processes played an important role in sorption of BPAF. Hydrogen bonds was the main driving force for the adsorption, and π–π stacking and hydrophobic interactions were probably extra important mechanisms to the adsorption of BPAF. The MWCNT have higher stability within eight removal–regeneration recycles and up to 95% of recovery could be obtained using ethanol elution. The results of the experiment verified effectiveness for the recovery and removal of BPAF from wastewater samples.

The interaction between olaquindox (OLA) and bovine serum albumin (BSA) was investigated using fluorescence, UV–vis absorption and circular dichroism (CD) spectroscopy. The results showed that the fluorescence quenching of BSA by OLA was a static quenching process induced by the formation of OLA–BSA complex. The binding constant of OLA–BSA complex was calculated to be 1.299 × 104 L mol−1 (293 K). The negative values of ΔH0 and ΔS0 indicated that hydrogen bond and van der Waals interactions played major roles in stabilizing the complex. Site probe competition experiments and number of binding sites (n) revealed that OLA could bind to site I in subdomain IIA of BSA, and the binding distance (r) was evaluated to be 3.643 nm according to Forster’s non-radiative energy transfer theory. The results of CD and three-dimensional fluorescence spectra suggested some conformational changes of BSA after OLA binding.

Multi-walled carbon nanotubes (MWCNTs) were used for the sorption of tetracycline (TC) from aqueous solution. A systematic study of the adsorption process was performed by varying pH, ionic strength, sorbent amount, sorption time and temperature. The adsorption mechanism is probably the non-electrostatic π–π dispersion interaction and hydrophobic interaction between TC and MWCNT. The adsorption efficiency could reach 99.8%, suggesting that MWCNT is excellent adsorbents for TC removal from water. TC adsorption kinetics were found that the equilibrium was reached within 20 min following the pseudo-second-order model with observed rate constants (k2) of 0.026–0.032 g mg−1 min−1 (at varied temperatures). The whole rate process appeared to be influenced by both intraparticle diffusion and boundary layer diffusion. The sorption data could be well interpreted by the Langmuir model with the maximum adsorption capacity of 269.54 mg g−1 (293 K) of TC on MWCNT. The mean energy of adsorption was calculated to be 0.029 kJ mol−1 (293 K) from the Dubinin–Radushkevich adsorption isotherm. Moreover, the thermodynamic parameters for the adsorption were estimated, and the ΔH° and ΔG° values indicated the endothermic and spontaneous nature of the sorption process.

The concession period is one of the most crucial variables influencing the success of a transportation project under the build-operate-transfer (BOT) procurement model. Since BOT transportation projects are characterized by irreversibility and uncertainty, project values tend to be underestimated by ignoring the value of the option to defer in the evaluation process, and thereby a long concession period is required by the concessionaire and a high subsidy is invariably paid by the government concerned when a project is financially nonviable. However, the existing net present value (NPV) method for making a concession period decision cannot properly capture the managerial flexibility value in BOT projects. In addition, the existing Nash bargaining model used in the concession period negotiation process cannot define an optimal concession period but can only narrow the interval of the concession period. This paper presents an alternative method for determining the optimal concession period by considering the investment in BOT-type transportation projects under dynamic uncertainty. In the proposed model, real options theory is used to identify an effective interval of concession period for a BOT transportation project, and Nash negotiation theory is applied to find the optimal value of the concession period. An actual transportation project in China is referred to as demonstrating the effectiveness of the proposed model.

Bisphenol AF (BPAF) was used as a model compound to investigate the binding mechanism between the endocrine disrupting compound and human serum albumin (HSA) using multispectroscopic techniques and molecular modeling method at the protein level. The results indicated that BPAF was indeed bound to HSA and located in the hydrophobic pocket of HSA on subdomain IIA through hydrogen bond and van der Waals interactions. The fluorescence quenching data showed that the binding of BPAF and HSA quenched the intrinsic fluorescence of HSA, and the static quenching constants were acquired.